Trees of the genus Gmelina are major afforested trees in tropical zones of the world, such as India and Southeast Asia Gmelina are also fast-growing trees whose woods are used for architectural materials, sculptural materials, pulps, fiberboards, plywoods, among other applications and whose barks, roots and fruits are used for medicines. Recent progress of plant tissue culture technique has enabled preservation of excellent varieties of many trees by tissue culture as genetic resources. Utilization of plant tissue culture technique has been expected for preservation, among other purposes of excellent varieties even of trees of the genus Gmelina. Generally, conventional techniques, such as afforestation by culturings, are not acceptable in attempts to propagate useful old trees. It is also understood that propagation of old trees is hard to conduct.
Recently, several research groups have been studying tissue culture techniques applied to trees of genus Gmelina to solve the problems so far encountered. In this connection, only two successful results have been reported up to now: J. C. Yang, G. Y. Tsay, J. D. Chung and Z. Z. Chon: Micropropagation of Gmelina arborea R. in Procedings of the SABRAO international symposium 29:213-218 (1992) and Crizald, E. N: Tissue culture of fast-growing trees in Sylvatrop 5(2); 123-137 (1980).
However, in these studies young plants germinated under aseptic conditions were used as materials. Thus regeneration and large-scale propagation of young plants from materials excised from mature trees containing a large amount of phenolic substances were not successfully carried out. Thus, development of an efficient propagation method using mature trees has been keenly desired.